1. Field of Invention
This invention is related to a scanner. More particularly, this invention is related to a scanner having a self-collection light source.
2. Description of Related Art
Over recent years, with the great development in digital technology, and the phenomenal progress achieved in Internet and multi-media technologies, the image data is usually preferred to be converted into a digital format for subsequent processing. Therefore, we can take a direct shot at an object with a digital camera, and extract the image information from a document or picture with an optical scanner, then convert such information into digital image data. This allows the users to display the images on computers or other electronic products for document display, optical character recognition (OCR), editing, storing, and outputting.
According to the method of inputting document images, the optical scanners can be categorized into several types: palm style scanner, sheet feed scanner, drum scanner and flatbed scanner, and so on. For a flatbed scanner, the document or picture being scanned is placed on top of a transparent platform. The scanning process is performed by driving an optical scanning chassis, so as to scan step by step over the documents or pictures to have the complete image. Therefore, a flatbed scanner includes not only an optical scanning chassis, but also a transmission assembly for moving the optical scanning chassis to complete the scanning of a document or a picture.
Referring to FIG. 1A and FIG. 1B together, FIG. 1A is a schematic diagram showing the operation of a conventional flatbed scanner, and FIG. 1B shows its transmission assembly. In this flatbed scanner, a transparent platform 110 is disposed at the top, and a back-and-forth movable optical scanning chassis 120 is disposed under the transparent platform 110. The optical scanning chassis 120 includes a light source component 130, a light source fixture 140, multiple reflectors 160, a lens 150 and a light sensor 170. The transmission assembly 180 includes a stepper motor 185, a supporting housing 195, a gear set 190, a transmission belt (not shown), and so on.
As shown in FIG. 1A, the light source 130 emits light to document 115 sitting on the transparent platform 110. The light beam is first reflected from the surface of the document 115, then enters the interior of the optical scanning chassis 120, and sequentially undergoes reflection by the reflector 160 and refraction by the lens 150, eventually received by the light sensor 170 mounted inside the optical scanning chassis 120. The light is then converted into digital signal for output, and recorded as the digital image data.
Next, referring to FIG. 1B, in the transmission assembly 180, a stepper motor 185 is implemented on the supporting housing 195 to provide the driving power. The driving power supplied by the stepper motor 185 is transmitted via the gear set 190, so as to allow the optical scanning chassis 120 to scan along a pre-defined direction to perform the scanning process of a document.
The structure of a conventional light source unit 130 is shown in FIG. 2. It includes a tube 210 and the electrodes 220 on both ends thereof. The inside of the tube 210 is coated with a fluorescent material (not shown), and mercury vapor and certain noble gases are filled inside the tube 210. As a voltage is applied across the electrodes 220 sitting at both ends of the tube, accelerated electrons are produced in tube 210. The electrons bombard the mercury vapor and the noble gases in tube 210, and excite them to their excited states. These excited molecules can emit ultra-violet light as they return to the ground state. A visible light is then generated as the ultraviolet light bombards on the fluorescent material inside tube 210. However, this type of structure in light source 130 cannot meet the development requirements of high speed scanning with low exposure time due to its scattering nature of the light output.